1. Field of the Invention
The present invention relates to a cassette data detecting apparatus of a system for loading a plurality of cassettes, which is incorporated in, e.g., a video tape recorder (to be referred to as a VTR hereinafter) or a digital audio tape recorder (to be referred to as a DAT hereinafter) and detects the presence/absence of a cassette or the presence/absence of a safety lug (erroneous erasure preventing lug) of a cassette.
2. Description of the Related Art
Recently, long TV programs have been increased in number, and the number of midnight broadcast TV programs has been increased after the start of satellite broadcasting. Therefore, the recording mode of VTRs is being changed to a mode capable of preforming timer or unattended recording or long-time recording.
Existing VTRs, however, can load only one tape cassette, and this limits a recording capacity in performing long-time recording or unattended recording. In addition, the dimensional standard of cassettes brings about limitations in the formation of large-capacity cassette tapes. In order to solve these problems, a VTR which can load a plurality of cassettes is proposed.
A VTR generally has a safety lug detecting apparatus for detecting the presence/absence of a safety lug. Conventional safety lug detecting apparatuses perform detection by inserting the distal end of a lever into a recess portion formed in the rear end face of a cassette when the cassette is placed in a predetermined loading position close to a rotary head drum. That is, a safety lug is formed in the recess portion, and a user snaps this lug off in order to obtain erasure prevention (recording inhibition). As a result, the distal end of a detecting lever enters the recess portion to activate a recording inhibiting function when the cassette is loaded. However, when the lug is not snapped, the detecting lever does not enter the recess portion. Therefore, since the recording inhibiting function does not operate, recording can be performed.
As described above, conventional safety lug detecting apparatuses detect the presence/absence of a lug after a cassette is placed in a predetermined loading position. Therefore, in the case of a VTR which can load a plurality of cassettes, it is impossible to determine whether recording can be performed before another cassette replaces the cassette loaded in a predetermined loading position. That is, in a system loading a plurality of cassettes, whether each of the cassettes is recordable cannot be determined until the cassette is placed in a predetermined driving position. This makes it meaningless to load a plurality of cassettes in order to perform long-time recording.
In addition, when a carrying unit capable of loading a plurality of cassettes is provided in a VTR, it is necessary to check data indicating whether a cassette is present or absent in each cassette loading position.